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A flippy disk (sometimes known as a "flippy") is a double-sided 5¼" floppy disk
Floppy disk

A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangle plastic shell....
, specially modified so that the two sides can be used independently (but not simultaneously) in single-sided drives. Use of "flippy" disks was most common during the 8-bit
8-bit

Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their address space is limited to 64 KBs. This is not a "natural law", however, so there are exceptions....
 home computer
Home computer

A home computer was a class of personal computer entering the market in 1977 and becoming common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles....
 era of the early-to-mid 1980s.

Generally, there were two levels of modifications:

A number of floppy disk manufacturers produced ready-made "flippy" media.






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A flippy disk (sometimes known as a "flippy") is a double-sided 5¼" floppy disk
Floppy disk

A floppy disk is a data storage medium that is composed of a disk of thin, flexible magnetic storage medium encased in a square or rectangle plastic shell....
, specially modified so that the two sides can be used independently (but not simultaneously) in single-sided drives. Use of "flippy" disks was most common during the 8-bit
8-bit

Eight-bit CPUs normally use an 8-bit data bus and a 16-bit address bus which means that their address space is limited to 64 KBs. This is not a "natural law", however, so there are exceptions....
 home computer
Home computer

A home computer was a class of personal computer entering the market in 1977 and becoming common during the 1980s. They were marketed to consumers as accessible personal computers, more capable than video game consoles....
 era of the early-to-mid 1980s.

Generally, there were two levels of modifications:
  • For Disk Operating Systems that did not use the index hole
    Hard sectoring

    Hard sectoring in a magnetic storage or optical disk data storage device is a form of Disk sectoring which uses a physical mark or hole in the recording medium to reference sector locations....
     in the disk to mark the beginnings of tracks, the "flippy" modification required only a new write-enable notch to be cut. For this purpose, specially designed single-square-hole hole punchers, commonly known as disk doublers, were produced and sold by third-party computer accessory manufacturers. Many users, however, made do with a standard (round) hole puncher and/or an ordinary pair of scissors for this job. The Apple II and Commodore DOS
    Commodore DOS

    Commodore DOS, aka CBM DOS, was the disk operating system used with Commodore International's Commodore International#Computers, 8-bit. Unlike most other DOS systems before or since—which are booted from disk into the main computer's own random access memory at startup, and executed there—CBM DOS was executed internally in t...
     were two of the many systems that could use such disks.
  • For disk operating systems that did use index sync, a second index hole window had to be punched in both sides of the jacket, and for hard sectored formats, an additional window must be punched for the sector holes. While cutting a second notch was relatively safe, cutting additional windows into the jacket was at great peril to the disk within.


A number of floppy disk manufacturers produced ready-made "flippy" media. As the cost of media went down, and double-sided drives became the standard, "flippies" became obsolete.

Special cases

  • At least one manufacturer created a diskette drive for the TRS-80
    TRS-80

    TRS-80 was Tandy Corporation's desktop microcomputer model line, sold through Tandy's Radio Shack stores in the late 1970s and early 1980s. The line won popularity with hobbyists, home users, and small-businesses....
     platform with two index read sensors so that the disk could be flipped over without the necessary index hole punch. Data written with these rare drives complicates conversions today for retrocomputing
    Retrocomputing

    Retrocomputing is a term used to describe the use of early computer computer hardware and computer software today. Retrocomputing is usually classed as a hobby and recreation rather than a practical application of technology; enthusiasts often collect rare and valuable hardware and software for nostalgia purposes....
     archivists due to the sector offset skewing: the sectors start earlier than they would using the standard index hole placement.


Two versions on one disk

  • During the time of single sided floppy disks some software manufacturers would use the two sides of one floppy disk to store two different copies of the same program. Each side would contain one copy of the program designed to be run on a different computer architecture. For instance several games were released that contained a Commodore 64 version on one side and an Apple II version on the other side of the disk. The same trick was used with TRS-80 software matching it with either Commodore 64 or Apple II versions in the same way. These releases were short lived however. When double sided floppy drives appeared this technique soon disappeared.


  • As an easter egg, the Apple II version of Karateka
    Karateka (computer game)

    Karateka is a 1984 computer game by Jordan Mechner, the creator of Prince of Persia. Karateka was Mechner's first hit game, and was designed while he was attending Yale University....
    , a 1984 computer game by Jordan Mechner
    Jordan Mechner

    Jordan Mechner is a game programmer, game designer, screenwriter and movie director. Mechner was born in New York, New York. He graduated from Yale University with a BA in Psychology in 1985....
     contained a second version placed on the flip side of the disk. If one put the disk into the drive upside-down, the game played identically to the first side, except that the game was displayed vertically flipped.